Special-purpose machinery is the set of processing and packing machines made for one trade, such as dairies, flour mills, tile works and medicine plants. A dairy machine cannot make tiles. Each trade has its own machine makers, and they sell a machine together with decades of service.
The reason for this is that each trade has its own process. A dairy must heat, cool and separate milk without letting germs enter. A flour mill must crush grain and sift it. A tile works must press powder and fire it in a kiln. A machine maker that knows one trade well can build better machines for it than a general maker can.
For instance, a mid-sized dairy buys a processing line for milk and curd. The maker designs the line, installs it and trains the staff. Over the next twenty years, the dairy buys spare parts, repairs and upgrades from the same maker. This is why makers value the aftermarket, and the service parts management software that handles it.
Such a line is usually sold as a turnkey project. The maker designs the whole line, builds it, installs it, tests it and hands it over, with a written guarantee of how many litres or kilograms it will process in an hour. The buyer pays in stages, and the project can take a year or more. The buyers are dairies, food processors, flour millers, tile makers, drug makers and similar plants. They choose the maker who has already built many lines for their trade, because a line that fails to reach its guaranteed output is costly.
There are three well-known branches. Food processing machinery covers dairy, pasta and chocolate. Ceramic machinery covers tiles and washbasins. Bioprocess and sterilisation equipment covers vessels that grow cells for medicines.
These machines use the parts of the rest of the line: pumps and valves, heaters and coding printers. They report their output to the MES.